Phased Development & Construction Sequencing

Figure 1 Consider temporary stabilization of lots after the utilities are installed, as areas seeded before utility installation will only be torn up and will need re-seeded.

​Land development for large residential subdivision projects with multiple sections can be difficult to manage in terms of sediment and erosion control. It is logistically challenging to stay on top of sediment control when there are so many moving parts and deadlines that need to be met to move on to the next step of development. For example, a delay in utility installation can set the whole project back. But you can stay ahead of the game to stay compliant with sediment and erosion control using construction sequencing and a phased approach. 

Proper planning is key. How can you begin grading a future section before knowing what the improvement plans will look like? Those future areas may need to be re-graded a second time when the improvement plans are developed, wasting time and money. No more than 50% of the overall project should be bare at any one time (Ohio EPA). The best way to achieve this is to have a phased approach. Limit site development and grading to one section at a time. Leave future sections undisturbed and protected by vegetation. This way, erosion is minimized, and sediment controls can be more effective and easier to maintain, protecting downstream neighbors, wetlands and streams.

Construction Sequencing and Phasing.
One thing we look for during a Stormwater Pollution Prevention Plan (SWP3) review, is if there is a phased construction sequence that looks something like this:
1. Installation of sediment and erosion controls prior to any upslope disturbance. In this stage, perimeter controls like silt fence or a mulch filter berm are essential. A gravel construction entrance of #2 gravel is also a must-have to prevent sediment track-out.
2. Tree clearing and preservation. Try to keep some of those mature trees. It will help you sell lots (a lot of lots!) and improve property values after all! Make sure to install orange fencing to keep construction vehicles away from trees and their root zones. Check out this Ohio EPA’s guidance on tree preservation here. Remember this saying with trees: “as above so below”. Expect the root system to mirror the size of the tree canopy so you don’t disturb the roots and kill that beautiful tree.
3. Grading. The sediment basin must be the first thing installed prior to any upslope disturbance to be able to accept sediment runoff from those upslope areas.  Don’t forget the floatable skimmer device! Learn more about sediment basins and skimmers here.
4. Roads, utilities, construction. During the construction phase, it is important to have lot controls in place to contain sediment on the lots. Curb filter socks and gravel entrances will help prevent track-out onto roads or running off into streams. Routine street sweeping throughout the subdivision’s internal roads will be required, at least once a week or more if needed. If the lot controls are working well, you might reduce street sweeping.

Figure 2 Street sweeping during dry spells may require dust control measures

5. Permanent Stabilization. Once construction is complete and areas are at final grade, it’s time for permanent stabilization. Be sure to re-incorporate that stockpiled topsoil back into the yards to improve stabilization and infiltration. That hard, compacted clay will surely put a damper on a gardener’s plans! Refer to Rainwater & Land Development Manual for more on stabilization techniques.
6. Walkthroughs and As-Built survey. Once the project is complete and stabilized with grass, schedule your final walkthrough to get any bond money back (provided the roads and sidewalks don’t need repaired). Remove any temporary sediment and erosion control measures like silt fence, inlet protection, remove the skimmer from the basin and convert the outlet structure to the post-construction water quality orifice design. Complete an as-built survey and send to the engineer of record of that municipality for review against the approved design.

Permitting
Any project that disturbs over one acre as part of a common plan of development needs an Earth Disturbing Permit. It’s always preferable and more manageable to break a large project into multiple phases. This also makes sense economically. Sometimes we will see an entire subdivision project of 100 acres or more cleared and graded up front. You have your equipment on site now, why not grade it all at the same time right? Wrong. This approach makes it very challenging and costly to maintain sediment and erosion controls as years go by until lots are sold and homes are built. Consider the possibility of an economic downturn or another 2008 housing crash. What if you spent a lot of money developing all this land up front, but are you having trouble selling the lots you developed and getting that return on investment? Don’t get phased out, phase your development! Learn more about minimizing your phased disturbance here.

In conclusion, you can phase your development by having proper planning, construction sequencing and grading one section at a time. It may save you time and money and can make sediment and erosion control easier and more effective. But don’t let it phase you too much! We are here to help! Reach out to Warren County Soil & Water Urban Team for any questions regarding permitting or sediment and erosion control guidance at 513-695-1337.
For more guidance and technical specifications, refer to Ohio EPA’s Rainwater & Land Development Manual.
​
By Justin Bedocs, Urban Specialist